1. Field of the Invention
The present invention relates to display technology, and more particularly, to organic light-emitting display devices.
2. Description of the Related Art
An active matrix (AM)-type organic light-emitting display device includes a plurality of pixels each including a pixel driving circuit including a thin-film transistor (TFT) formed of silicon. Amorphous silicon or polycrystalline silicon is used in the TFTs.
An amorphous silicon TFT (a-Si TFT) used in a pixel driving circuit has a low electron mobility of 1 cm2/Vs or less since a semiconductor activation layer that constitutes a source, a drain, and a channel is formed of a-Si. Recently, the a-Si TFT has been replaced with a polycrystalline silicon TFT (poly-Si TFT). The poly-Si TFT has higher electron mobility and higher stability with respect to light than the a-Si TFT. Accordingly, poly-Si is suitable for use in an activation layer of a driving and/or switching TFT of an AM organic light-emitting display device.
Poly-Si may be formed using various methods. The poly-Si formation may be largely divided into a method of directly depositing poly-Si and a method of depositing a-Si and crystallizing the a-Si.
Examples of the direct deposition method include chemical vapor deposition (CVD), Photo CVD, hydrogen radical (HR) CVD, electron cyclotron resonance (ECR) CVD, plasma enhanced (PE) CVD, and low pressure (LP) CVD.
Examples of the crystallization method in which a-Si is deposited and then crystallized include solid phase crystallization (SPC), excimer laser crystallization (ELC), metal induced crystallization (MIC), metal induced lateral crystallization (MILC), and sequential lateral solidification (SLS).
FIG. 1 is a schematic view of a crystallization device 9 for crystallizing deposited a-Si. The crystallization device 9 includes a laser generator 91 for generating a laser beam L, a focusing lens 92 for focusing the laser beam L emitted from the laser generator 91, and a reduction lens 93 for reducing the laser beam L that has passed through the focusing lens 92 by a given magnification.
In the laser generator 91, a laser beam L that is not processed is emitted from a light source and passes through an attenuator (not shown) so that intensity of energy of the laser beam L is controlled, and the controlled laser beam L is irradiated through the focusing lens 92.
Meanwhile, an x-y stage 94 on which a substrate 10 on which a-Si layer is deposited is located corresponding to the laser generator 91. In this case, in order to crystallize the entire area of the substrate 10, the x-y stage 94 need to be horizontally moved.
A method of crystallizing silicon using a conventional crystallization device as described above will now be described in detail. In order to deposit crystalline silicon on a substrate, an insulating layer (called “buffer layer, not shown) is formed on the substrate, and an a-Si layer is deposited on the buffer layer and crystallized with the application of a laser beam to the deposited a-Si layer. Typically, the a-Si layer is deposited on the substrate by CVD.
However, when crystallization is performed using a laser beam, the entire area of the substrate, that is, both a pixel area and a circuit area are crystallized. In the pixel area, a channel area, a storage area, and an emission area are all crystallized. In addition, due to the limited width of the laser beam, crystallization is performed while moving the laser generator or the substrate with respect to each other. However, organic light-emitting display devices are manufactured as large devices, and accordingly, the area to be crystallized is increased. Therefore, maintenance expenses for generating a laser beam by a laser generator are increased.
The foregoing discussion is to provide background information relating to the invention disclosed in this application and does not constitute an admission of prior art.